The single 'Wolves,' which he co-wrote with American singer Selena Gomez and released later in the year 2017, was a financial hit and peaked in the top 10 in more than 20 different nations. Along with topping the Billboard Dance/Electronic Songs list, it also topped the charts in Latvia, Poland, and Hungary.
Marshmello and rapper Lil Peep collaborated on a postmortem song titled 'Spotlight' in January 2018. Only after consulting with Peep's mother, who had asked that her son's unreleased musical composition be made available as widely as possible, did he decide to release the single. A month later, 'There 2,' which was made by Marshmello and regular partner Slushii, was made into a single.
Continuing his winning trend, he released 'Friends' in 2018 with British musician Anne-Marie. The song rose to number eleven on the Hot 100, becoming his highest-charting hit until October 2018. Along with getting double-platinum and triple-platinum certifications from Australia and Canada, it also gained a single-platinum certification in Belgium, Germany, New Zealand, the United Kingdom, and the United States.
He also worked with the British band Bastille to create 'Happier' in 2018, which went on to become his single with the highest position on the Billboard Top 100 charts. This is the only song to date that has spent up to 69 weeks on the US Dance/Electronic Songs Chart.